week calculation follows only ISO?

[jcompagner]

Prerequisites

• I have searched for duplicate or closed issues.
• I have validated my setup against the latest version on StackBlitz.
• I have read the contributing guidelines.

Describe the issue

January 2028 with startOfWeek = 0 looks like this:

but in the US (or en-US locale) it should be:

this is because of the rule what the first week is

for ISO that is where the first 4 days are in (so because iso starts on Monday, the Thursday should at least 1 Jan., so that Thursday -> Sunday are the 4 days in the new year)
But for US the rule is where day 1 is in.. so first of January.

this information is now provided by most current browsers: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale/getWeekInfo

For chromium its nog getWeekInfo() as a function but it is:

const uk = new Intl.Locale("en-UK")
uk.weekInfo

which the gives you firstDay and also minimalDays

StackBlitz fork

https://stackblitz.com/edit/tempus-dominus-v6-repl-fif9uy?file=example.js

What operating system(s) are you seeing the problem on?

Windows, macOS, Linux

What browser(s) are you seeing the problem on?

Microsoft Edge

What version of are you using? You can find this information from the sample StackBlitz.

6.7.11

What your browser's locale? You can find this information from the sample StackBlitz.

nl but the problem is showing for the us locale

[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• tempus-dominus-v6-simple-setup (Open reproduction)
• tempus-dominus-v6-repl-fif9uy (Open reproduction)